How does climate affect levels and types of vegetation?

The relationship between vegetation and climate and weather is absolute. Each is entirely dependent on the other. Climate is a product in no small measure of ocean currents, which cover most of the Earth’s surface. While vegetation exists under many conditions, including on the ocean floor, it cannot survive under all conditions. Arid climates such as exist in the American southwest and even more dramatically in regions like northern Africa and the Arabian Peninsula – sights of the two largest deserts in the world – are completely devoid of vegetation for thousands of square miles. The dryness of the climates and of the soils are inhospitable to vegetation, leaving them, as the desert of the Arabian Peninsula is called, the “Empty Quarter.”

Climate affects vegetation – and it is not surprising that the polar-regions are similarly devoid of plant life – but the relationship also works in reverse, with plants contributing to the type of climate. Plants absorb water and release energy that helps determine the type of climate a particular region experiences. The moisture released into the atmosphere by plants contributes to the climate, while the moisture level in the climate in turn contributes back to the Earth’s ability to foster the growth of vegetation. Additionally, and of particular importance in this age of increased concern about greenhouse gases and their effects on the Earth’s atmosphere, some types of plants absorb carbon monoxide, a build-up in the atmosphere of which would prove toxic to human beings.

Whether plants are more important to the climate or the climate is more important to plants is a subject for discussion, but there is no question that it is a symbiotic relationship and that the effects of climate on vegetation is enormous. Clearly, as anyone who lives in a region that experiences a dramatic change-of-seasons every year has observed, weather and climate changes directly affect plant growth. One recent study determined that the global pattern of vegetative growth has changed over the last several decades consistent with climate changes. To quote from one 2013 article on the relationship between climate and vegetation:

“In a striking and perhaps unexpected development, the [research] team found that while vegetation has declined south of the equator, it has increased in the northern hemisphere. The climate is what governs the seasonal activity of vegetation. In the humid mid-latitudes, temperature is the largest factor influencing plant growth.” [See “Climate Change Responsible for Global Vegetation Change,” Climate News Network, April 7, 2013]

Which points to further evidence of the effect of climate on vegetation: the presence of the world’s densest concentrations of jungle on and near the equator. The heat and humidity characteristic of those latitudes explains the locations of the Amazon and central African rainforests, while, as mentioned earlier, the freezing temperatures associated with the polar regions are completely inhospitable to plant life.

The relationship of climate and weather to vegetation is established fact. Whether the balance of responsibility of one for the other leans towards climate or towards vegetation is less certain, but prevailing wisdom points to the overriding influence of climate in determining levels and types of plant life, and not the other way around.